[ka-Map-users] Drawing polygon in ka-map

[Stephen Woodbridge]

Lorenzo Becchi wrote:
> Hi Stephen,
> I've lost this e-mail because was not in the list, sorry.
> I'm answering you publicly to share this thinking, hope it's ok for you.

Yes, no problems.

> your questions:
>> Would it be possible to get you to bubble polygon creation/editing up 
>> to the top of your stack :) Or more generally, geometry, instead of 
>> just polygons. It would be nice if this feature would allow the user to:
>>
>> create:
>> select locations using the mouse on the map and
>> "save" the polygon back to the server in map coordinates (ie: lat/lon).
>>
>> edit:
>> get a polygon from the server via unique id or unique id via a query
>> optionally request the polygon be locked
>> allow vertices to be added, deleted, moved
>> "save" the polygon back to the server or
>> "save as new" the polygon back to the server
>> bonus points: suport some special case polygones:
>> 1) square or rectangle, optionally rotated about a corner
>> 2) circle and N-side polygon, based on center, radius or radius point
>>
>> unlock:
>> release a lock before it times out if requested above.
>>
>> delete:
>> request a polygon on the server be deleted via unique id or query
> 
> 
> 
> This ideas are in my and Andrea's mind since quite a long time. I know 
> we are not the only ones.
> We scanned all technologies to see how to do this and to do it strong, 
> mostly universal.
> Vectorial drawings are the system to use.
> The system PG has developed is a good starting point to do this but 
> there are some doubts:
> 1) browser support for vectorial graphics is not fully stable and not 
> universal (not standard). PG had to play with different technologies to 
> manage his API for ka-map.

Yes, this is a problem.

> 2) in this situation only "little" polygons or lines can be managed. 
> "little" is a relative concept and in this case it starts to be more 
> relative. Maybe it's OK to desing a 20  vertices  polygon but what about 
> a country border? how can you offer a system that works just with 
> 20-100-1000  vertices and not for 10.000? 
> this in not depending from your skills but from browser support and 
> development.
> more over there are other problems related moving 10.000 point over the 
> internet.

Well, there are a lot of applications that can work with "smaller" 
polygons. And the infrastructure to support a small polygon is basically 
the same for a large polygon, with the problems you have already noted.

So one way to deal with the limit on vertices, would be only allow 
editing of a portion of a geometry, instead of the whole geometry, as a 
thought. the user would select a geometry and it would be cached server 
side, and the user would select a location near the edge and then some 
number of points would get loaded to the client for manipulation. these 
could then be saved to the cached geometry and the scenario repeated. 
Finally the user could save the cached/modified geometry or abandon it.

This would be workable (if not ugly), but would allow us to do something 
now rather than wait for some undetermined future. Anyway if is just an 
idea off the top of my head.

> 3) I've seen something nice done with flash that has a good vectorial 
> management system. The problem? flash is proprietary, that's enough for 
> me. more other you need a plug-in to use it in your browser and 
> connection problems are the same of any other technology.
> 
> So, my sentence is: browsers are not yet mature to do this.
> (or maybe, I'm not yet mature to do this)

Yes, I think the browsers are not yet mature, but when is the real 
question here?

> Now I have to say that I'm always looking for a way to mind this gap. 
> Once I'll be ready I'll surely let you know.
> :-)
> 
> anyway there are many experimental ideas we are working on.
> One dream is to create a Web Interface for some/many GRASS functions 
> using ka-Map framework.
> 
> hope my answer doesn't look so simplistic.

No, you are very clear about the problems, and they are very real 
issues. I think the challenge for us is to find good work-a-rounds  so 
we can move forward with building tools. Clearly if the browsers are 
going to solve these problems in the short term, then wait is not a 
problem, but I have not seen anything on that oneway otr the other.

> thanks for asking and commenting
> ciao
> Lorenzo
> 

Thank you for your thoughtful response.

Best regards,
   -Steve

> 
> On 08/ago/06, at 14:50, Stephen Woodbridge wrote:
> 
>> Lorenzo Becchi wrote:
>>> Elene, we are working on it.
>>> We'll be please if you'll help us testing  and debugging it.
>>> Please be patient a while more...
>>> you can trace CVS updates with:
>>> http://cia.navi.cx/stats/project/ka-map
>>> anyway, main changes will be commented on the list.
>>
>> Hi Lorenzo,
>>
>> I know you have been busy contributing LOTS of great stuff to ka-map. 
>> I particularly like kaExplorer. Thanks. I took a vacation in the 
>> Dominican Republic a few years ago. It is a great place to visit, I 
>> hope you are enjoying the sun and the culture.
>>
>> Would it be possible to get you to bubble polygon creation/editing up 
>> to the top of your stack :) Or more generally, geometry, instead of 
>> just polygons. It would be nice if this feature would allow the user to:
>>
>> create:
>> select locations using the mouse on the map and
>> "save" the polygon back to the server in map coordinates (ie: lat/lon).
>>
>> edit:
>> get a polygon from the server via unique id or unique id via a query
>> optionally request the polygon be locked
>> allow vertices to be added, deleted, moved
>> "save" the polygon back to the server or
>> "save as new" the polygon back to the server
>> bonus points: suport some special case polygones:
>> 1) square or rectangle, optionally rotated about a corner
>> 2) circle and N-side polygon, based on center, radius or radius point
>>
>> unlock:
>> release a lock before it times out if requested above.
>>
>> delete:
>> request a polygon on the server be deleted via unique id or query
>>
>> It would be up to the user of the functionality to write the 
>> polygon.php or geometry.php script to implement the backend. But I 
>> would be happy to write a simple reference server-side script to 
>> support this functionality and say store and retrieve the data from 
>> postgis. By using postgis, it would be simple to include the data in 
>> the database as a layer in the mapfile for display and query.
>>
>> Please let me know if you are interested. I would be happy to work up 
>> a spec for the server scripts and work with you to define the data 
>> exchange for the ajax requests. I know this is relatively small 
>> effort, but it is something that I can do to support this effort.
>>
>> Best regards,
>>   -Stephen Woodbridge
>